The difference is that Dwarf Fortress only released on Steam because they had financial worries due to some health scares. They decided to release it on steam and charge for it but they wanted to deliver a major overhaul of the UI to justify selling it, even though people wanted to pay them for years.
DF has been in development for 20 years but it’s essentially a full game that they’ve been making better. Yeah it’s buggy (they simulate so goddamn much of course it’ll have bugs), but it’s at least a full experience that you can replay many times and never have the same experience.
Star Citizen does not deliver a full game, it’s just a glorified tech demo. It’s cool tech, but it’s not worth playing in my opinion.